בראשית, פרק ל׳, פסוק ט׳

After establishing her place in the family and giving birth to four sons, Leah experiences a sudden halt in childbirth. Following the birth of her son Judah, she simply stops having children [ביאור שטיינזלץ]. Instead of accepting this pause, she takes a highly unusual step and introduces another woman into her husband's life. Though Zilpah is known as a maidservant, she is actually Laban's daughter. According to local custom, daughters born to a concubine were commonly referred to as maidservants [דעת זקנים]. Furthermore, Jacob's marriage to these women is permitted because, prior to the giving of the Torah, lineage was determined by the mother. Therefore, daughters born to different mothers were not legally considered sisters, removing any restriction against marrying the same man [פענח רזא].

Commentators wonder about the nature of this action. It is highly uncommon for a woman to willingly bring another wife to her husband, especially when she is not barren and has already been blessed with children [רמב״ן, ביאור יש״ר, ברכת אשר על התורה]. The primary approach among commentators is that Leah acts out of prophetic insight. The Matriarchs are aware that Jacob is destined to establish twelve tribes. Leah desires to ensure that the majority of these sons are born either directly to her or to someone under her authority, ensuring her sister Rachel does not surpass her in the total number of children [רמב״ן, הטור הארוך, ביאור יש״ר, ברכת אשר על התורה].

Beyond family dynamics, a broader national motive drives this decision. The ancestors know that the land of Canaan is promised to their descendants. Since Abraham and Isaac did not have many children, Jacob and his wives are eager to multiply their family line so they can eventually inherit the land upon their return in the fourth generation. Recognizing this deep need for many sons, Leah acts swiftly to offer her maidservant, preventing a situation where Jacob might feel compelled to marry a foreign woman to achieve this goal [רמב״ן, הטור הארוך, ביאור יש״ר, רד״ק].

A completely different perspective suggests a personal and moral motivation between Leah and her maidservant. In this view, Leah notices that Zilpah is jealous of Rachel's maidservant, Bilhah, who has already been given to Jacob. Feeling that she is wronging Zilpah by withholding a similar status from her, Leah decides to give her to Jacob as a wife to correct this inequality [העמק דבר].